You say that you would like to “come clean.” That’s an expression commonly used for people who have done something wrong. What are your feelings about going OTD? Are you uncomfortable with yourself?
I can say that I disagree with Popa, you probably have great parents and it’s okay to not want to tell them something that would hurt their feelings.
Can you find a middle ground, where you keep kosher and Shabbos (or at least some parts of Shabbos)? You would be able to be comfortable with where you are, yet you wouldn’t feel a need to tell your parents anything as you are still keeping the faith. Good luck with your decision.